Furnace control



March 16,1926; 1,576,754

* E. MCLEAN FURNACE CONTROL Original Filed Dec. 10. 1921 4 Sheets-Sheet1' B LER Pm ssuns m INVENTOR.

ATTORNEYS E. M LEAN FURNACE CONTROL March 16 1926.

Original Filed Dec.

10, 1921 4 Sheets-Sheet 2 INVENTOR.

MA TTORNEYS Z W Z 4/ 44 W Z Y .z y If 2 y a Z W j f 2 W 6 & WZZ$ z W Z WMarch 16 1926.

E. M LEAN FURNACE CONTROL 4 Sheets-Sheet 5 Original Filed Dec. 10. 1921WITNESS:

March 16 1926.

E. M LEAN FURNACE CONTROL l0. 19%1 4 Sheets-Sheet 4 ,1 76.

'IIIIIIIIIIIIII/IIIIIIIIZ Original Filed Dec.

% A TTORNEYS Patented Mar. 16, 1926.

UNITED STATES PATENT ounce.-

EMBURY MOI-EAR, F BROOKLYN, NEW YORK, ASSIGNOR TO THE ENGINEER COI-PANY, OF NEW YORK, N; Y., A CORPORATION OF NEW YORK.

FURNACE CONTROL.

Application filed December 10, 1921, Serial No. 521,318. Renewed April22, 1925.

provements in furnace control, and more particularly to that type offurnace fired with fluid fuel. 1 g

The object of the invention is'to provide means whereby asupplyof airnecessary for combustion w1ll be efiiciently and properly controlledatall times so as to bear the proper relation to the supply of oil orfluid fuel fed to the furnace during a given period.

The invention consists in the improvements to be more fully describedhereinafter,

and the novelty of which will be particular- -ly pointed out anddistinctly claimed.

have fully and clearly illustrated a preferred embodiment of myinvention in the accompanying drawings to be taken-as a part of thisspecification, and wherein- Figure 1 is a view in side elevation, partlyin section, of a furnace having one embodiment of my invention appliedthereto.

, Fig. 2 is a similar .view showing another embodiment of the same.invention.

Fig. 3 is a section on the line 33 of Fig. 1 and Fig. 2. I I so Fig. 4is a view in front elevation, partly iIn section, of a controlling meansshown in Fig. 5 is a section on the line 55 of Fig. 4. v

$0 Fig. 6 is a view in rear elevation, partly in section, of acontrolling means shown in Fig. 2. I

Fig. 7 is a section onthe line 7-7 of Fig; 6

-- 4 Fig. 8 isaplan view of the lower ortion of the controller shown inFigs. 6 an 7.

Fig. 9is'a top lanview of the top member of the control er shown inFigs. 6, 7 and Fig. 10 is .a' longitudinal central section through thecontroller shown in Figs. 6, 7, 8 and 9, l

Fig. 11 is a longitudinal section through a control device forregulating the supply of 4 boiler furnace fired by fluid fuel, andhaving means for controlling the draft or supply of air for combustion.

In thedrawings, the furnace is shown as consisting of a side wall 1,front wall 2, rear wall 3, and an intermediate or bridge wall 4,

a steam drum of a steam boiler being indicated generally at 5. Betweenthe front wall 7 2 and the bridge wall 4 is located the combustionchamber 6, located over a substan tially horizontal partition 7 extendinfrom the front wall to the said bridge wa and from one side wall to theother, so as to pro- 7 vide an. air inlet chamber 8 beneath saidpartition. An area or portion of said partition may be open-work orchecker-work structure so as to provide a plurality of'openings fromwhich airmay flow from the chamber 8 to the furnace chamber 6, said areabeing substantially co-e'igtensive with the size of the flame when theburner is working with a large vollime of oil. By reference to Fig.

3, it will be seen that the checker-work is of flaring form, thetapering sides of which are provided by imperforatedportions 10 of saidpartition at the forward corner of the furnace, the outwardly inclinededges 11 of said imperforate portions defining the forward boundaries ofthe flaring checker-work portion. In the present embodiment. the saidflaring edges 11 extend from a point ad jacent the center of the frontwall to 8. int substantially midway the length of the Side 05 walls ofthe furnace, so that the checkerwork extends from said boundariesrearwardsto the bridge wall lengthwise 01' the furnace, and the entirewidth "of the furnace at points in rear of the points at which said 1boundaries merge with said side walls; It will be seen that the area ofthe 'open work portion of the partition 7 conforms substantially to themaximum form of the flame in the furnace chamber. r

The furnace is-also provided with a 'suit-. able draft-controllingmeans, in this instance, consisting of-a'suitable outlet stack 12through which the products of combustion find exit, the area of thepassage throu h the stack being controlled by a suitable damper v13pivoted, as at 14, on the stack, in any suitable manner.

The furnace is provided with any suitable nozzle or burner 15 forfeeding fluid fuel to the furnace, and in which the fuel is atomized bysteam or air under pressure fed to the burner simultaneously with thefluid fuel. The burner or nozzle is preferably located in the frontportion of the furnace chamber above the partition 7 and central of thetransverse width of the" furnace chamber, and'over the forward portionof the open-work area of said partifrom a suitable source is fed to theburner er through the pi es 17 and 19 is controlled by a regulator, sown generall at 21, in Figs. 1, 2 and 3, and specifica ly, in Fig.

11, operating valves in the fluid fuel and steam pipes, the valve inthelatter being located between the hand-valves20; This re%1lator may beof any suitable type capa 1c ofadjustment so as to automaticallyregulate theamou'ntof oil fed to the burner tofore describe steam withinthe chamber22: I

of the spring 36 may be regulated by ad-' in accordance with the steampressure of the boiler, and also the quantity of steam fed to theburnerto atomizethe oil.

Referring particularly to Fig.11, I have shown a wel -known type ofregulator for this purpose; the same consisting lindrical chamber 22having iaphragm heads 23, 24 sealin the chamber, the latter beingconnecte by a pipe 25 with a source of steam at boiler pressurei Overthe diaphragm 23 is a plate 26" supporting a frame 27 connected at'itsuper end, in any suitable manner to a'va ve body or casing 28 located inthe steam ipe between the valves 20, as stated, said ody having a valveI seat 29 with which "cooperates a valve 30 co'nnected' to a stem 31guided by a stufling-box 32, and a sleeve 33, thev latter being threadedin the said frame 27, as at 34. The valve stem 31 is connected to aplate 35 resting1 on'the diaphragm 23, hereis an expansion spring .36;thefe'ndsof which respectively abut the said plate35 and an abutment'37resting against the'lower end of said sleeve '33, the functionof'saidspring being to urge the valve, 30 -toward open position inopposition to the ressure of he pressure justing said screw sleeve 33and consequent of a cy- Surrounding the stem 31 ly the position of saidplate 37 so that the latter maybe adjusted relative to the plate 35 tocompress or relieve the compression of the spring 36..

A construction similarzto the above is provided for regulating the,uantity of fluid fuel, and includes a valve ody or casing 38 in the pipe17 having a seat 39 having a passage controlled by a valve 40, thelatter beingconnected to a stem 41 uided through a stufling box 42correspon ing to the stuffing-box 32, heretofore described, andsupported by 'a frame 43,'which is in turn supported by a plate v44similar to the plate 26, heretofore described; I The stem 41 is guidedthrough an adjustable screw sleeve 45 threaded through a portion of theframe, as at 46, and carrying an abutment plate 47 against which abutsone end of a coil spring 48 coiledabout the said stem 41, and the otherend of which spring is connected to the plate 49 on the outer face ofthe diaphragm 24. This spring 48 normally urges the valve 40 towardsopen position in opposition to the steam pressure within the chamber 22tending to close the valve. By adjustment of the elements 33 and 46,heretofore described, the relative area of the opening in the steamsupply pipe 9 and the oil supply pipe 17 may be regulated in accordancewith a given steam pressure in order to determine theamounts orquantities of oil and steam fed to the boiler.

Thefluid fuel fed' from the burner or nozzle 15 to the furnace chamber,this being' under ressure, is in a form which results in a: ame whichiseither substantial- 'ly cone-shape or fan-shape, according to the vt.pe of .burner used.j .It is desirable that t eyair enteringthe'f'urnace chamber be admitted over an area: conforming as nearg aspossible to the form or area of the ame, in order 'that'the best resultsbe obtained as regards com lete combustion.

I- will now descri e improved means whereby the draft of the furnace orthe air supplied thereto for combustion is varied or controlled by theoil fed to the furnace. This means includes a regulator, shown in thepresent instance as being'of the same general'construction as shown anddescribed in my prior Patent No. 1,071,771, dated September 2, 1913. Oneadaptation of this regulator forthe present furnace is shown in Figs. '4and 5, wherein 5O designates a rectangular frame set in an opening inone of the said walls of the furnace and providing an opening betweenthe furnace chamber and the external atmosphere. In

this rectangular frame is arranged a swing- 1 ing' rectangular plate 51fulcrumed at a point adjacent its lower end, as at 52 to the sidemembers ofv the-said frame, said fulcrum being located preferably at, orclosely lll) so that said plate will remain stationary on its pivot atany point to which it may be moved. In order to assure the axis beingthrough the center of gravity of the plate, a weight 53 issupported onthe lower portion of said plate, said weight being adjustably supportedand held by upper and lower nuts 54:, 55 on threaded rods 56, secured tothe lower portion of the plate 51. The movement of the plate on itsfulcrum is opposed by up er and lower tension springs 57, 58, the formerbeing connected at its :-lower end to a projection 59 on the lower endof the swinging plate, and at its opposite end, to an adjustableanchorage consisting of .an'eye 60 on a threaded shank 61 1 extendingslidably through a bracket 62 se- The movements of this vide a curedrigidly to the side of the frame 50, said threaded shank beingadjustably held by means of upper and lower nuts 63, whereby the tensionof the spring 57 may be adjusted.

movement of the plate, and also to balance the action of the draftpressure in the furnace, in a manner to be presently described. pressureregulator are employed to control t e positionof the stack damper 13 soas to control the rate of outflow of furnace gases through the stack. 1

-In order to accom lishthis result, I projiilot valve 68 aving an inlet69 connected y a pipe 70with a source of fluid 'under pressure, and acombined inlet and outlet 71 connected by a pipe 72 to the lower end ofanoperating'cylinder 73 containing a piston .74 connected to a pistonrod 75,

which in turn is connected by a flexible connection 76 with a lever arm77. for operating the damper, said flexiblefoonnection being passed overan intermediate'guide pulley 78. The pilot valve is provided with ,apiston valve 79 connected loosely to. a'bracket arm 80 on the lowerportion of the swinging plate 51. The pipe is connected by a pipe 81 tothe up or endof the cylinder 73, above described: Thepipe 70 containshand-valves 82, 83 on opposite sides of the connection with said .pipe.81,.and the pipe 72 contains a hand-valve 84. The

" pilot valve casing is provided with an escape opening 85 at its lowerend.

The operation of .said pilot valve is to control the flow of fluidpressure to'and from the-lower end of the cylinder 73 in order tooperate the piston 74 to control the damper 13. On the lever 77 is aweight 86 normally tending to hold the damper in open position. Theconstruction of this pilot valve is specifically shown in Fig. .4, but Ido not deem it necessary to describe the same with greater detail, as itis of well-known construction, and specifically does not form a part ofmy present invention.

On the frame 50 is a bracket arm 87, upon the lower end of which issupported a pressure chamber 88 formed by a rigid side wall 89,;and anopposing diaphragm wall 90 against which engages a plunger head 91 on aplunger stem 92, having one end in engagement with one member 93 of abellcrank lever fulcrumedas at 94 on a bracket 95, and the other member96 of which lever is pivotally connected at 97 to the lower end of thethreaded shank 65. The diaphragm chamber isconnected by a pipe 98 withthe pipe 17 leading to the burner 15, so that the pressure of oil in thepipe 17 is com-- municated to the diaphragm chamberand acts against thediaphragm 90 and the plunger head 91. The pressure of oil against theplunger-head'91' is opposed by an expansion Spring 99, one end ofwhich'is located in the spring head 100 engaging the opposite side ofthe bell-crank lever 93 from that which en ages the plungerrod 92, andthe other en of which spring isseated in a spring seat 101 which abutsan adjusting screw 102 threaded through a fixed abutment 103 supportedby the rods 104 at- ;tachedto the diaphragm chamber structure.

The screw 102 IS adjustable to vary the force of the spring 99, and maybe held in adjusted position by a jam-nut 104. 3

When the pressure of oil is at the minimum 'for firing the furnace,- thetension of the springs '57, 58, is adjusted so that the excess tensionon the lowerspring over the upper spring added to the draft pressure onthe inside of the plate is just suflicient ressure on the to balance theatmospheric 7 outside of the plate; where y theplate is heldin neutralposition, as shown in'Fig; 5,

. and the pilot valve GS iB mainta-in'ed in position to cut off flow offluid under pressure to the bottom of the cylinder 7 3, The loweradjusting nut 67 is then set against the bottom. of the bracket 66, andthe upper ggju stingnut 67- is movedQtoward the eye i to 've play to thethreaded shank 65 throng the said bracket. The feed of fluid fuel tothefburner is then increased to the maximum pressure desired, andthispressure exerted on the diaphragm 90p'ushes the plunger head 91.andjpl-unger rod 92. outward toward the right of Fig, 4 against theforce of the spring 99 moving the bell-crank in a direction to increasethe tension on the lower spring 58. The adjusting screw 61 similarparts, to which reference may is then turned until the bracket and theplate 51 are pulled outward enough to cause the damper 13 to opensufficiently to give the desired amount of draft in the furnace chamber6 for a maximumsupply of oil. The action of the spring 99 opposing thediaphragm will now hold the bell-.

crank controlling the tension on the lower spring 58, in such positionthat eve pressure of oil to the burner intermediate between the minimumand maximum of the regulator will automatically holdthe flue damper 13in a position to give a draft in the furnace chamber 6 that will givethe desired air supply for the fuel being fed to the furnace at thattime. The spring 99 should be of such proportions that for the range ofvariation of pressure of oil to the burner it will give the desiredtravel to the threaded shank to give the desired variations in tensionof the lower spring 58 to control the draft to the desired amount forminimum pressure of oil supplied to the burner, and 'for maximumpressure of oil supplied to the burner. In the form of the inventionshown in Figs. 2 and 6 to 10 inclusive, the operation of the regulatoris controlled by the rate of flow of oil passing to the burner asdistinguishedfrom control by pressure of oil fed to the burner, asheretofore described. In this form of the invention, I employ a plateregulator, such as heretofore described, and in view of the similarityof the structure I do not repeat the description as to features whichare in common, but have applied similar reference numerals to e made bythe description previously g ven. Upon a suitable bracket 105 issupported a regulator of my invention for controlling the operation'ofthe swinging plate in accordance with variations in the rate of flow ofoil or other fluid fuel fed to the burner. This regulator is shownspecifically in Figs. 6 to 10 inclusive, whereini106 designates a lowerhalf or member of a diaphragm chamber, the upper half of which is shownat 107, said members being connected by headed bolts 108 and nutsthereon, and said members clamping between them a flexible diaphragm 109shutting of! communication between said members; except as hereinafterdescribed. Integral with the. lower member is an inlet connection 110having a port 111 leading to'an opening 112 through the flange of themember 106 leading into a, passage 113 in the wall of the upper member107,

said passage 113 communicating with the s ace in said ulpperimemberabove the said aphragm. T ed to that. ortion of the pi e 17 of Fig. 2(corresponding to the pi e 1 heretofore described) leading from t e pump16. Connected' to the lower member 106 is an outlet e connection 110 isconnect-.

connection 114 (Fig. 8) opening) into the lower chamber of the deviceslow the diaphragm 109,- said connection being connected to a pipe 17leading from said reguinternal bore 119 of the valve, which inturncommunicates with a passage 120 leading into the member 106 beneath thediaphragm 109. In order to provide for a tight fit, the valve 117 ispreferably tapered and fitted to a correspondingly tapered bore in thecasing 116, and is urged to its seat by a spring 121 surrounding a stem122 on said valve and at one end abutting a packing gland123 threaded.into the casing 116, and at its other end abutting the upper end of thesaid valve 117. The valve is provided with a head 124 adapted to be enaged by a wrench or other suitable means, y which it may be rotated.Connected to the diaphra m 109, in a suitable manner, 'as at 125, is oneend 126 of a rod 127 extending upwards through a stufling-box 128 in theupper wall of the member 107, the upper end. of said rod 127 beingfitted with an eye :piece 127 and connected by a link 129 to onethreaded member 130 of a turn-buckle 131, the other threaded member 132of which is connected to one end of a tension spring 133, the oppositeend of which is connected to a bracket arm 134 rigidly fixed to theswinging plate adjacent the axis thereof. Around the rod 127 and betweenthe stuffing box 128 and, the shoulder of the eye piece 127 is placedacompression 5 ring 128. The means for connecting the ro 127 to thediaphragm109 consists of a dished plate 135 having a flange 136 securedby a fluid tight joint to the lower face of the diaphragm 109, by meansof screws 137, extending through said flange and packing washers 138between the said flange and the diaphragm, and threaded into a washer orring 139 on the upper side of the diaphragm. The dished portion of theplate 135 extends u wards through a central to ening in the diaphragmand has a centra opening 140 through which the rod 127 extendspthe rodhaving beneath said plate an enlargement or head 1410f greater diameterthan the opening. in the said plate, so that the rod and plate areconnected. The. underside of the plate is closed against leakage by aplate 142'held in place by the screws 137 When there is a minimum rateof flow of oil to the barrier the nut 131 is adjusted to increase thetension on the'spring 133 pulling the plate outward, which moves the Vdamper towardsitsopen position. As soon as the damper is movedsuflicientl to give" ave? the desired draft in the furnace c mber 6 togive the requisite quantityof air for proper combustion of, the volumeor oil then fed to the furnace-,1 thenut 131 is left in that position.The flowfof'oil' to the burner is then increased to the maximum rate offlowrequired, with the restriction valve 117'wide open, "This valve isthen gradually closed until the restriction is sufcient to cause adifference in pressure between the upper and lowermember, so that thedia hragm .is pushedfldownwa'rd, and acting't rough the rod 127 thetension of the spring 133 is increased, pulling the plate outward andmoving the damper 13 toward open position. The restriction valve 117 isthen moved towards its closed position until app'roximatel the'shape andarea of thethe draft. in the furnace chamber 6 is sufficient to give-thedesired amount ofair fo'r themaximum rate of flow of oil fed to thefurnace. For any intermediate rate of flow between the minimum and themaxi-3 ward movement ofthe rod 127.

The fluid] fuel fed from the burner or nozzle to the furnacechamber 6bein under pressure is in the form which resu ts in a .flame whichiseither substantially coneshaped or fan-shaped, according to the t ofburner employed. It is desirable 'thatt e air entering the'furnacechamber 6 be admitted over an area conformm as nearly as possible to theform or area 0 the flame, in order that the best results be obtained asregards complete combustlon. My invention rovides an efficient means forregulat-.

ing t e area of air distribution, and for this provide means forcontrolling the ur I realfl f the o en-work portion of the partition 7throng which theair flows fromthe space 8 to the chamber 6, so that sendarea will conform substantially to the area of the flame, and willsupply a iluantity of an desirable for combustion. or this purpose Idivide the chamber 8 into a pluralityofairchambers, each preferabl havng anmdeaving outlets up- 7 ndent alr supply and sv ards into thefurhace chamber 6 through that rtion of the open-work partition 7 immeiately over-the partlcular chamber beneath said partition. In thepresent embodiment, I referably divide chamber 8 :z'into three suc airsupply chambers, and do 7 exten wall, asshown at 7 The inner ends ofsald partitions 7 are connected by outwardl directed end partitionsv 7with the si e walls of the furnace, respectively. The par-v titions and7 extend from the floor of the furnace to the underside ofthe partition7, so as to form three separate independent chambers, It will be seenthat by the arrangement of partitions 7" and 7", the space beneath thepartition 7 is divided into a central flaring chamber '2' and two wingcom partments 7 said central chamber being;

flame when t e burner is being operatedat: a relatively low pressure,and the air through the open work portion of the partition 7 from thewing compartment 7 being available for an increased areaof the flamewhen the burner is operated at relatively high pressures. It will thusbe seen that am able to control the area of air sup: plied throu h theartition -7 in order. to conform su' stantia y to the area of the flamewhen the burner is o erated at different pressures, As stated,preferably pro vide separate means for controlling the supply of air toeach of the chambers 7 and- 9, such means preferably consisting ofdampers 8*, the same being pivoted, respectively, in the passage betweenthe inner ends of the walls 7, and openings 7 in the said partitions 7.In the resent embodiment, I desire it understood, however, that myinvention, as re ards the method of air distribution toconorm to thearea of the flame, is not limited to any articular means suitablebearings, carrying operating levers 8, for swinging the dampers. Anysuitable manual operating means may be used for this purpose. Thecentral damper is mounted on a shaft 8 connected by a universal joint 8with one or both of the said shafts 8",. so as to move all three of saiddampers in'unison. 'Th6 connection between the central dam erfand theouter dampers is so adl sted closed, the mantral damper W111 bepartlally open, so as to admit air to the central chamber 6, but as-theouter dampers are moved toward open position, the inner damper. willbemov'ed to increase the area of the opening controlled thereby to thecentral at when the .outer. dampers are chamber 6. Air is admitted tothe front portion of the furnace beneath the partition and in front ofthe walls 7, through an air duct 9 in the front wall of the furnace. Thegeneral construction is the same as that shown and described in mycopending application, Serial No. 391,779, filed June 25, 1920, but inthe present instance the automatic control of the air dampers shown insaid prior application is omitted, and said dam rs are set by hand asstated herein, to give suflicient opening to admit sufficient air, theamount of which is controlled by the automatic regulator which controlsthe draft in the furnace.

While I have shown an eflicient means for suppl ing air to thecombustion chamber distributed in accordance with the shape of theflame, I desire it understood my present invention is not limited-tosuch means but that any suitable means may be employed for supplying airto the combustion cham- So far, as I am aware, I am the first to utilizea characteristic of the flow of fluid fuel to the furnace, andillustrated either as ressure'or rate of flow for varying the action ofa means controlled by the furnace gas pressure, which in turn controlsthe supply of air to the furnace.

What I claim and desire to secure by Letters Patent of the United Statesis 1. In a fluid fuel fired furnace in combination, means for feedingfluid fuel to the furnace means for varying a characteristic of theflow'of fluid fuel fed to the furnace, means for controlling the supplyof air to the furnace for combustion, means controlled by furnace gaspressure for operating said means for controlling the supply of air, andmeans capable of actin in accordance with a characteristic of t e flowof the 'fluid fuel to the furnace for varying the action of said meanscontrolled by furnace gas pressure.

2. In a fluid fuel fired furnace in combination, means for feeding fluidfuel to the furnace means for varying the rate of flow of fluid fuel fedto the furnace, means for controlling the supply of air to the furnacefor combustion, means controlled byfurnace gas pressure for o cratingsaid means for controlling the supp yof air, and means capable of acting'in accordance with variations in the rate of flow of fluid fuel fed tothe furnace'for varying the action of said means; controlled by'furnacegas pressure.

3 In a fluid fuel fired furnace in combinatlon, means for feeding" fluidfuel to the furnace, means for varying a characteristic of the flow offluid fuel fed to the furnace, means for controlling the supply of airto "the furnace for combustion, means controlled by furnace gas pressurefor operating said means for controlling the su ply of air, a regulatingspring for controlling the action of said means controlled by furnacegas pressure, and means capable of' acting in accordance with variationsin a characteristic of the fluid fuel fed to the furnace for varying theaction of said spring.

4. In a fluid fuel fired furnace, in combi nation, means for feedingfluid fuel to the furnace, means for varying a'characteristic of theflow of fluid fuel fed to the furnace, means for controlling the supplyof air to the furnace for combustion, a member exposed to internalfurnace pressure and to atmospheric pressure, an adjustable resist anceopposing atmospheric pressure on said member, and means capable ofacting in accordance with variations in a characteristic of the flow ofthe fluid fuel fed to the furnace for varying said resistance.

5. In a fluid fuel fired furnace in combination, means for feeding fluidfuel to the furnace, means for varying the rate of flow of fluid fuelfed to the furnace, means for controlling the supply of air to thefurnace for combustion, a member exposed to internal furnace pressureand to atmospheric pressure, an adjustable resistance opposingatmospheric pressure on said member, and means capable of acting inaccordance with variations in rate of flow of fluid fuel fed to thefurnace for varying the action of said resistance.

6. In afluid fuel fired furnace in combination,,means for feeding fluidfuel to the furnace, means for varying the rate of flow of fluid fuelfed to the furnace, means for controlling the supply of air to thefurnace for combustion, a member exposed to internal furnace pressureand to'atmospheric pressure, and adjustable resistance opposing atmospheric pressure on said member, and means capable of acting inaccordance with variations in rate of flow of fluid fuel fed to thefurnace for increasing said resistance when the rate of flow of oilincreases and decreasin said resistance when the rate of flow of oidecreases.

7. In a fluid fuel fired furnace in combination, means for feeding fluidfuel to the furnace, means for varying the rate of flow of fluid fuelfed to the furnace, means for controlling the supply of air to thefurnace for combustion, a swinging plate exposed on one face to furnacegas pressure and on the other face to the atmosphere, an adjustableresistance opposing atmospheric pressure on said plate, and meanscapable of acting in accordance with variations of the rate of flow offuel fed to the furnace for automatically adjusting said resistance inaccordance with variations in the rate of flow of fluid;

fuel fed to the furnace.

8 a fluid fuel fired furnace in combination, means for-feeding fluidfuel .to the furnace, means for varying the rate of flow of fluid fuelfed to the furnace, means for controlling the supply of air to thefurnace for combustion, means controlled by furnace gas pressure foroperating said means for controlling the supply of air, a regulatingspring for controlling the action of said means controlled by furnacegas pressure, and means capable of acting in accordance with variationsin-the rate of flow of fluid fuel fed to the furnace for varying theaction of said spring.

9. In a fluid fuel fired furnace in combination, means for feeding fluidfuel to the furnace, means for varying a characteristic of the flow offluid. fuel fed to the furnace, means for controlling the supp-1y of airto the furnace for combustion, means controlled by furnace gas pressurefor operatingv said means for controlling the supply of air, aregulating spring for controllin the action of said means controlledbyurnace gas pressure, and means capable of acting in accordance withvariations in a characteristic of the fluid fuel fed to the furnace forinof the flow of fluid fuel fed to the furnace,-

means for controlling the supply of air to the furnace for combustion, amember exposed to internal furnace pressure and to atmospheric pressure,a spring opposin the movement of said member under atmosp eric pressure,and means capable of acting in accordance with variations in acharacteristic of the fluid fuel fed to the furnace for varying theresistance of said spring.

11. In a fluid fuel fired furnace in combination, means for feedingfluid fuel to the furnace, means for varying the rate of flow of fluidfuel fed to the furnace, means for controlling the supply of air to thefurnace for combustion, a swinging plate exposed on one face to furnacegas pressure and on the other face to the atmosphere, a s ring resistingatmospheric pressure on the plate, and means capable of acting inaccordance with variations in the rate of flow of fluid fuel fed to thefurnace for varying the resistance of said spring.

12. In a furnace, means for controlling the supply of air to the furnacefor combustion, means controlled by furnace gas pressure for operatingsaid means for controlling the supply of air, and means forautomatically varying the action of said means controlled by furnace gaspressure.

In testimony whereof, I have hereunto signed my name.

EMBURY MOLEAN.

